1. Field
The present disclosure relates to natural gas systems, and more, particularly to a system and processes for filling natural gas storage tanks.
2. Related Art
In today's modern society there has been a growing option of utilizing liquid natural gas (“LNG”) as fuel. In general, LNG is an attractive fuel for vehicles such as, for example, automobiles, trucks, and buses, aircraft, boats, and maritime vessels due to the low cost of LNG.
A major drawback to LNG, however, is that LNG is a cryogenic fluid and more importantly a very strong greenhouse gas. As such, LNG, as a cryogenic fluid, has a boiling point of approximately −162° C. that is well below the normal environmental ambient temperatures on Earth and any vented (i.e., released) LNG into the environment will quickly boil-off into gaseous natural gas (“GNG”) that will dissipate into the atmosphere as a strong greenhouse gas. This is a problem because in order to properly fill a LNG storage tank with LNG, the LNG storage tank (which is a cryogenic tank) must first be pre-chilled to a temperature that is approximately equal to the temperature of the LNG that is being used to fill the LNG storage tank. A problem with many known techniques to pre-chill the LNG storage tank include filling the LNG storage tank with cold LNG and then venting the LNG to the atmosphere to chill the LNG storage tank. Since LNG is a strong greenhouse gas, the known techniques are very undesirable to the environment and additionally by venting the LNG directly to the atmosphere, the system experiences a significant loss in potential work or potential energy. As such, there is a need for a pre-chill system for use in reducing boil-off of LNG when filling an LNG storage tank that overcomes the problems of the prior art.